X-cut lithium niobate crystal growth method and temperature field structure

Abstract

The application discloses a lithium niobate crystal growth method and a temperature field structure, and defines that an X axis extends upwards. The temperature field structure used in the method comprises a heat preservation structure and a crucible. The heat preservation structure and the crucible are both elliptical cylinders with an open upper end and a closed lower end. In use, the crucible is placed in the heat preservation structure, the central axes of the crucible and the heat preservation structure coincide, the heat preservation structure has a major axis a1 and a minor axis b1, the crucible has a major axis a2 and a minor axis b2, the major axis of the heat preservation structure and the major axis of the crucible both extend along a Y axis direction, and the minor axis of the heat preservation structure and the minor axis of the crucible both extend along a Z axis direction. The lithium niobate crystal grown by the lithium niobate crystal growth method is an elliptical cylinder. The application solves the problem that crystals are prone to cracking in the prior art, and improves the success rate of X axis lithium niobate crystal growth.

Description

Technical Field

[0001] This invention relates to the field of crystal growth technology, and in particular to an X-cut lithium niobate crystal growth method and temperature field structure. Background Technology

[0002] Lithium niobate crystals possess excellent electro-optic effects, virtually unrestricted intrinsic modulation bandwidth, low optical insertion loss, low power consumption, and good device stability, thus attracting widespread attention from researchers. Integrated optical paths based on lithium niobate single-crystal thin films have overcome key performance parameters such as transmission loss and optical confinement inherent in traditional titanium diffusion and proton exchange waveguides. Scientists have already achieved various active and passive integrated optoelectronic devices in the laboratory with ultra-low transmission loss, ultra-low half-wave voltage, and ultra-small size.

[0003] Lithium niobate single-crystal thin films are peeled from lithium niobate wafers. Lithium niobate crystals belong to the trigonal crystal system, and the largest component γ in the electro-optic coefficient matrix is... 33 ~30.9 pm / V@632 nm. To achieve on-chip integration of lithium niobate, an X-axis wafer is required. Waveguide coplanar electrodes are used, and an electric field is applied along the Z-axis of the crystal to utilize the electro-optic effect γ. 33 On the one hand, the fabrication of integrated chips requires semiconductor microfabrication technology. Currently, the mainstream semiconductor production line is 8 inches, so 8-inch X-axis lithium niobate crystals are the cornerstone of the integrated optoelectronic chip industry chain.

[0004] However, the X-axis is a non-rotational symmetry axis, and the growth rates of different crystal planes on the growth interface are different, making it the most difficult direction to grow. For a long time, China has only been able to supply a small number of 3-inch and 4-inch X-axis lithium niobate crystals, and some of these still use the technique of horizontally carving out small-sized X-axis crystal rods from large-sized Z-axis crystals. Especially as the crystal size increases, the horizontal carving technique becomes increasingly impractical. Therefore, breaking through the key technologies for the industrialization of large-sized X-axis lithium niobate crystals is a crucial foundation for building an integrated optoelectronic chip industry chain.

[0005] The growth of X-axis lithium niobate crystals is carried out in a temperature field structure, which includes a crucible and a heat preservation structure. The existing temperature field structure has a cylindrical heat preservation structure and a small hole on one side of the heat preservation structure for observing the growth. At the same time, crystal rotation or crucible rotation and lifting are applied to increase forced convection and ensure the uniformity of the temperature gradient distribution. The resulting lithium niobate crystal is cylindrical.

[0006] Existing temperature field structures are most commonly used for growing Z-axis lithium niobate crystals. Z-axis lithium niobate crystals are isotropic, meaning their properties and growth rates are similar along the X and Y axes. A perfectly symmetrical insulation structure provides an isotropic temperature distribution, perfectly suited to the characteristics of Z-axis crystals, thus significantly improving crystal quality. However, using existing temperature field structures to grow X-axis lithium niobate crystals is problematic. The different growth rates along the X-axis make traditional cylindrical symmetrical insulation structures and crucibles unsuitable for X-axis crystal growth. When pulling lithium niobate crystals along the X-axis, the large difference in growth rates between the Z and Y axes easily leads to anisotropic nucleation and twinning; simultaneously, high thermal stress and crystal cracking occur, resulting in extremely low crystal growth success rates and hindering industrial production. Summary of the Invention

[0007] This invention provides an X-cut lithium niobate crystal growth method and temperature field structure to solve the technical problems in the prior art where X-axis lithium niobate crystals are prone to anisotropic nucleation, twinning, and crystal cracking, resulting in a low crystal growth success rate.

[0008] This invention provides an X-cut lithium niobate crystal growth method and temperature field structure:

[0009] An X-cut lithium niobate crystal growth method is disclosed for growing X-axis lithium niobate crystals, where the X-axis extends upwards. The temperature field structure used in this method includes a heat preservation structure and a crucible. Both the heat preservation structure and the crucible are elliptical cylinders with open tops and closed bottoms. In use, the crucible is placed inside the heat preservation structure, with the central axes of the crucible and the heat preservation structure coinciding. The heat preservation structure has a major axis a1 and a minor axis b1, and the crucible has a major axis a2 and a minor axis b2. The major axes of both the heat preservation structure and the crucible extend along the Y-axis, and the minor axes of both the heat preservation structure and the crucible extend along the Z-axis. The lithium niobate crystal grown by this X-cut lithium niobate crystal growth method is an elliptical cylinder.

[0010] Furthermore, the ratio of the major axis a1 to the minor axis b1 of the heat-insulating structure is equal to the ratio of the major axis a2 to the minor axis b2 of the crucible.

[0011] Furthermore, the ratio of the major axis a1 to the minor axis b1 of the thermal insulation structure is d, and 1.1≤d≤1.5.

[0012] Furthermore, the growth rate along the Y-axis during the growth of the lithium niobate crystal along the X-axis is V. Y The growth rate along the Z-axis is V. z ,d=V Y V Z .

[0013] Furthermore, the difference between the long axis of the insulation structure and the long axis of the crucible is a = a1 - a2, where 2cm ≤ a ≤ 5cm.

[0014] Furthermore, during the growth process, the lithium niobate crystal is pulled along the X-axis at a pulling speed of V. t 0.2mm / h≤V t ≤1mm / h.

[0015] Furthermore, during the growth of lithium niobate crystals, neither the crucible nor the crystal rotates, and the crystal is observed from directly above the temperature field structure.

[0016] Furthermore, the insulation structure includes an elliptical cylinder and a cylinder bottom connected to the lower end of the cylinder. The cylinder includes a quartz layer, an insulation cotton layer, and a corundum layer, and the cylinder bottom includes an insulation cotton layer and a zircon sand layer.

[0017] Furthermore, the quartz layer, the thermal insulation layer, and the corundum layer of the cylinder are arranged sequentially from the outside of the cylinder to the inside of the cylinder. The bottom of the cylinder includes two layers of thermal insulation and two layers of zircon sand. The bottom layer of the cylinder is the thermal insulation layer, and the top layer is the zircon sand layer. The thermal insulation layer and the zircon sand layer of the bottom of the cylinder are arranged alternately.

[0018] A temperature field structure for growing X-cut lithium niobate crystals is disclosed, which is the same as the temperature field structure in the aforementioned X-cut lithium niobate crystal growth method. This temperature field structure is used to grow X-axis lithium niobate crystals, with the X-axis defined as extending upwards. The temperature field structure includes a heat-insulating structure and a crucible. Both the heat-insulating structure and the crucible are elliptical cylinders with an open top and a closed bottom. In use, the crucible is placed inside the heat-insulating structure, with the central axes of the crucible and the heat-insulating structure coinciding. The heat-insulating structure has a major axis a1 and a minor axis b1, and the crucible has a major axis a2 and a minor axis b2. The major axes of both the heat-insulating structure and the crucible extend along the Y-axis, and the minor axes of both the heat-insulating structure and the crucible extend along the Z-axis. The lithium niobate crystal grown by this X-cut lithium niobate crystal growth method is an elliptical cylinder.

[0019] Furthermore, the ratio of the major axis a1 to the minor axis b1 of the heat-insulating structure is equal to the ratio of the major axis a2 to the minor axis b2 of the crucible.

[0020] Furthermore, the ratio of the major axis a1 to the minor axis b1 of the thermal insulation structure is d, and 1.1≤d≤1.5.

[0021] Furthermore, the growth rate along the Y-axis during the growth of the lithium niobate crystal along the X-axis is V. Y The growth rate along the Z-axis is V. z d=V Y V Z .

[0022] Furthermore, the difference between the long axis of the insulation structure and the long axis of the crucible is a = a1 - a2, where 2cm ≤ a ≤ 5cm.

[0023] Furthermore, the insulation structure includes an elliptical cylinder and a cylinder bottom connected to the lower end of the cylinder. The cylinder includes a quartz layer, an insulation cotton layer, and a corundum layer, and the cylinder bottom includes an insulation cotton layer and a zircon sand layer.

[0024] Furthermore, the quartz layer, the thermal insulation layer, and the corundum layer of the cylinder are arranged sequentially from the outside of the cylinder to the inside of the cylinder. The bottom of the cylinder includes two layers of thermal insulation and two layers of zircon sand. The bottom layer of the cylinder is the thermal insulation layer, and the top layer is the zircon sand layer. The thermal insulation layer and the zircon sand layer of the bottom of the cylinder are arranged alternately.

[0025] The beneficial effects of this invention are as follows: The X-cut lithium niobate crystal growth method of this invention takes into account the growth habits of X-axis lithium niobate crystals and designs a temperature field structure suitable for X-axis crystal growth. By setting both the insulation structure and the crucible in the temperature field structure as elliptical cylindrical structures, and extending the major axis of the insulation structure and the crucible along the Y-axis growth direction of the lithium niobate crystal and the minor axis along the Z-axis growth direction of the lithium niobate crystal, the larger major axis and the smaller minor axis can respectively match the faster growth rate of the lithium niobate crystal on the Y-axis and the slower growth rate on the Z-axis. This allows the grown X-axis lithium niobate crystal to grow naturally without compression, resulting in an elliptical cylindrical shape. This elliptical cylindrical shape of lithium niobate crystal has a uniform internal density distribution, making it less prone to anisotropic nucleation and twinning phenomena. At the same time, the crystal is less prone to cracking, thereby improving the crystal growth success rate.

[0026] In addition, based on the characteristics of lithium niobate crystal growth, this invention has formulated the major and minor axis ratio parameters of the elliptical heat preservation structure and the crucible structure to ensure the stable growth of the X-axis crystal under controllable conditions as much as possible. This can reduce the possibility of anisotropic nucleation of the X-axis crystal, reduce the risk of polycrystalline formation and cracking, and improve the yield. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a top view of the temperature field structure for growing X-cut lithium niobate crystals according to an embodiment of the present invention;

[0029] Figure 2This is a schematic diagram of the AA section of the temperature field structure for growing X-cut lithium niobate crystals according to an embodiment of the present invention;

[0030] In the diagram: 1. Thermal insulation structure; 11. Quartz layer; 12. Thermal insulation cotton layer; 13. Corundum layer; 14. Zirconium sand layer; 2. Crucible; 3. Lithium niobate crystal. Detailed Implementation

[0031] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the invention.

[0032] In the description of this invention, it should be understood that the terms "longitudinal," "radial," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0033] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0034] Example 1 of the present invention provides a temperature field structure for the growth of X-cut lithium niobate crystals, as follows: Figures 1 to 2 As shown, this temperature field structure is used to grow lithium niobate crystals along the X-axis. The X-axis is defined as extending upwards, and the lithium niobate crystal 3 grown using this temperature field structure is an elliptical cylinder. This temperature field structure includes a heat-insulating structure 1 and a crucible 2. Both the heat-insulating structure 1 and the crucible 2 are elliptical cylinders with open tops and closed bottoms. In use, the crucible 2 is placed inside the heat-insulating structure 1, with the central axes of the crucible 2 and the heat-insulating structure 1 coinciding. The heat-insulating structure 1 has a major axis a1 and a minor axis b1, and the crucible 2 has a major axis a2 and a minor axis b2. The major axes of both the heat-insulating structure 1 and the crucible 2 extend along the Y-axis, and the minor axes of both the heat-insulating structure 1 and the crucible 2 extend along the Z-axis.

[0035] like Figure 1 and Figure 2 As shown, the insulation structure 1 includes an elliptical cylinder and a bottom connected to the lower end of the cylinder. The bottom is an ellipse with the same cross-sectional size as the cylinder. The cylinder includes a quartz layer 11, an insulation cotton layer 12, and a corundum layer 13. The bottom includes an insulation cotton layer 12 and a zircon sand layer 14. Specifically, the quartz layer 11, the insulation cotton layer 12, and the corundum layer 13 of the cylinder are arranged sequentially from the outside of the cylinder to the inside. The bottom includes two layers of insulation cotton 12 and two layers of zircon sand 14. The bottom layer is an insulation cotton layer 12, and the top layer is a zircon sand layer 14. The insulation cotton layer 12 and the zircon sand layer 14 are alternately arranged at the bottom. In other embodiments of the present invention, the number of layers of the insulation structure 1, as well as the material and thickness of each layer, can be set according to actual needs.

[0036] The crucible 2 is a platinum crucible 2. The only difference between the structure of the crucible 2 and the platinum crucible 2 in the prior art is the cross-sectional shape; that is, the prior art uses a cylindrical crucible 2, while this invention uses an elliptical cylindrical crucible 2. The crucible 2 includes an annular crucible body and a crucible bottom connected to the lower end of the annular crucible body. In this invention, the cross-section of the annular crucible body is elliptical.

[0037] In this embodiment, the ratio of the major axis a1 to the minor axis b1 of the insulation structure 1 is equal to the ratio of the major axis a2 to the minor axis b2 of the crucible 2. The ratio of the major axis a1 to the minor axis b1 of the insulation structure 1 is d, and 1.1 ≤ d ≤ 1.5. For the X-axis lithium niobate crystal growth method, d = 1.2 is preferred. Of course, in other embodiments, a reasonable value of d can be set according to the growth conditions of lithium niobate crystals under different growth environments. The growth rate along the Y-axis during X-axis lithium niobate crystal growth is V. Y The growth rate along the Z-axis is V. z ,d=V Y V Z .

[0038] In this embodiment, the difference a between the major axis of the heat-insulating structure 1 and the major axis of the crucible 2 is a = a1 - a2, where 2cm ≤ a ≤ 5cm. In other embodiments, the required difference a can be set according to the growth conditions of the lithium niobate crystal.

[0039] This invention discloses an X-cut lithium niobate crystal growth method. This method employs the aforementioned temperature field structure for X-cut lithium niobate crystal growth. The X-axis lithium niobate crystal grown by this method is an elliptical cylinder, with its central axis extending along the X-axis. The cross-sectional shape of the elliptical cylinder lithium niobate crystal perpendicular to the X-axis is elliptical, with the major axis being 'a' and the minor axis being 'b'. Here, the X-axis is defined as extending upwards.

[0040] The temperature field structure used in this method includes a heat preservation structure 1 and a crucible 2. Both the heat preservation structure 1 and the crucible 2 are elliptical cylinders with an open top and a closed bottom. In use, the crucible 2 is placed inside the heat preservation structure 1, with the central axes of the crucible 2 and the heat preservation structure 1 coinciding. The heat preservation structure 1 has a major axis a1 and a minor axis b1, and the crucible 2 has a major axis a2 and a minor axis b2. The major axes of the heat preservation structure 1 and the crucible 2 both extend along the Y-axis, and the minor axes of the heat preservation structure 1 and the crucible 2 both extend along the Z-axis. The lithium niobate crystal grown by this X-cut lithium niobate crystal growth method is an elliptical cylinder.

[0041] In this method, the ratio of the major axis a1 to the minor axis b1 of the insulation structure 1 is equal to the ratio of the major axis a2 to the minor axis b2 of the crucible 2. The ratio of the major axis a1 to the minor axis b1 of the insulation structure 1 is d, and 1.1 ≤ d ≤ 1.5. For the X-axis lithium niobate crystal growth method, d = 1.2 is preferred; however, in other embodiments, a reasonable value of d can be set according to the growth conditions of the lithium niobate crystal under different growth environments. The growth rate along the Y-axis during X-axis lithium niobate crystal growth is V. Y The growth rate along the Z-axis is V. z ,d=V Y V Z .

[0042] In this method, the insulation structure 1 includes an elliptical cylinder and a bottom connected to the lower end of the cylinder, wherein the bottom is an ellipse with the same cross-sectional size as the cylinder. Figures 1 to 2 As shown, the cylinder body includes a quartz layer 11, a thermal insulation layer 12, and a corundum layer 13, and the bottom of the cylinder includes a thermal insulation layer 12 and a zircon sand layer 14. Specifically, the quartz layer 11, the thermal insulation layer 12, and the corundum layer 13 of the cylinder body are arranged sequentially from the outside of the cylinder body to the inside of the cylinder body. The bottom of the cylinder body includes two layers of thermal insulation layer 12 and two layers of zircon sand layer 14. The bottom layer of the bottom of the cylinder body is the thermal insulation layer 12, and the top layer is the zircon sand layer 14. The thermal insulation layer 12 and the zircon sand layer 14 of the bottom of the cylinder body are arranged alternately. In other embodiments of the present invention, the number of layers of the thermal insulation structure 1, as well as the material and thickness of each layer, can be set according to actual needs.

[0043] The crucible 2 is a platinum crucible 2. The only difference between the structure of the crucible 2 and the platinum crucible 2 in the prior art is the cross-sectional shape; that is, the prior art uses a cylindrical crucible 2, while this invention uses an elliptical cylindrical crucible 2. The crucible 2 includes an annular crucible body and a crucible bottom connected to the lower end of the annular crucible body. In this invention, the cross-section of the annular crucible body is elliptical.

[0044] This invention employs the Czochralski method to grow X-axis lithium niobate crystals, that is, to pull lithium niobate crystals along the X-axis direction. During crystal growth, the pulling speed along the X-axis is V. tThe flow rate is 0.2 mm / h ≤ Vt ≤ 1 mm / h. Furthermore, during the growth of the lithium niobate crystal, neither the crucible 2 nor the lithium niobate crystal rotates, and the crystal is observed from directly above the temperature field structure. The temperature field structure of this invention has a uniform height around it, ensuring a stable internal temperature distribution and providing stable and favorable conditions for crystal growth.

[0045] In this embodiment, the X-cut lithium niobate crystal growth method of the present invention further includes an automatic control program for the constant diameter stage. This automatic control program for the constant diameter stage is prior art. In prior art, the diameter of the lithium niobate crystal to be grown can be automatically set in the control program. In this invention, the diameter R of the lithium niobate crystal is set, R = , where a represents the major axis of the elliptical cylindrical lithium niobate crystal, and b represents the minor axis of the elliptical cylindrical lithium niobate crystal.

[0046] The present invention provides a method for growing X-axis lithium niobate crystals, taking into account the growth habits of X-axis lithium niobate crystals and designing a temperature field structure suitable for X-axis crystal growth. Specifically, the insulation structure 1 and the crucible 2 in the temperature field structure are both set as elliptical cylindrical structures, and the major axes of the insulation structure 1 and the crucible 2 extend along the Y-axis growth direction of the lithium niobate crystal, while the minor axes extend along the Z-axis growth direction of the lithium niobate crystal. In this way, the larger major axis and the smaller minor axis can respectively match the faster growth rate of the lithium niobate crystal on the Y-axis and the slower growth rate on the Z-axis, allowing the grown X-axis lithium niobate crystal to grow naturally without compression. The grown lithium niobate crystal has an elliptical cylindrical shape, and the internal density distribution of this elliptical cylindrical lithium niobate crystal is uniform.

[0047] In addition, based on the characteristics of lithium niobate crystal growth, this invention has formulated the major and minor axis ratio parameters of the elliptical heat preservation structure 1 and the crucible 2 structure to ensure the stable growth of the X-axis crystal under controllable conditions as much as possible. This can reduce the possibility of anisotropic nucleation of the X-axis crystal, reduce the risk of polycrystalline formation and cracking, and improve the yield.

[0048] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method for growing X-cut lithium niobate crystals, characterized in that, For growing X-axis lithium niobate crystals, the X-axis is defined to extend upwards. The temperature field structure used in this method includes a heat preservation structure (1) and a crucible (2). Both the heat preservation structure (1) and the crucible (2) are elliptical cylinders with open tops and closed bottoms. In use, the crucible (2) is placed inside the heat preservation structure (1). The central axes of the crucible (2) and the heat preservation structure (1) coincide. The heat preservation structure (1) has a major axis a1 and a minor axis b1. The crucible (2) has a major axis a2 and a minor axis b2. The major axes of the heat preservation structure (1) and the crucible (2) both extend along the Y-axis direction. The minor axes of the heat preservation structure (1) and the crucible (2) both extend along the Z-axis direction. The lithium niobate crystal grown by this X-cut lithium niobate crystal growth method is an elliptical cylinder. The difference between the major axis of the heat preservation structure (1) and the major axis of the crucible (2) is a = a1 - a2, and 2cm ≤ a ≤ 5cm.

2. The method for growing X-cut lithium niobate crystals according to claim 1, characterized in that, The ratio of the major axis a1 to the minor axis b1 of the insulation structure (1) is equal to the ratio of the major axis a2 to the minor axis b2 of the crucible (2).

3. The method for growing X-cut lithium niobate crystals according to claim 2, characterized in that, The ratio of the major axis a1 to the minor axis b1 of the thermal insulation structure (1) is d, and 1.1≤d≤1.

5.

4. The method for growing X-cut lithium niobate crystals according to claim 3, characterized in that, The growth rate along the Y-axis during the growth of lithium niobate crystals on the X-axis is V. Y The growth rate along the Z-axis is Vz, d = V Y V Z .

5. The method for growing X-cut lithium niobate crystals according to any one of claims 1-4, characterized in that, During the growth of lithium niobate crystals, the lithium niobate crystals are pulled along the X-axis at a pulling speed of V. t 0.2mm / h≤V t ≤1mm / h.

6. The method for growing X-cut lithium niobate crystals according to any one of claims 1-4, characterized in that, During the growth of lithium niobate crystals, neither the crucible (2) nor the crystal rotates, and the crystal is observed from directly above the temperature field structure.

7. The method for growing X-cut lithium niobate crystals according to any one of claims 1-4, characterized in that, The insulation structure (1) includes an elliptical cylinder and a bottom connected to the lower end of the cylinder. The cylinder includes a quartz layer (11), an insulation cotton layer (12), and a corundum layer (13). The bottom includes an insulation cotton layer (12) and a zircon sand layer (14).

8. The method for growing X-cut lithium niobate crystals according to claim 7, characterized in that, The quartz layer (11), the thermal insulation layer (12), and the corundum layer (13) of the cylinder are arranged sequentially from the outside of the cylinder to the inside of the cylinder. The bottom of the cylinder includes two layers of thermal insulation layer (12) and two layers of zircon sand layer (14). The bottom layer of the cylinder is the thermal insulation layer (12), and the top layer is the zircon sand layer (14). The thermal insulation layer (12) and the zircon sand layer (14) of the bottom of the cylinder are arranged alternately.

9. A temperature field structure for growing X-cut lithium niobate crystals, characterized in that, The temperature field structure is the temperature field structure in the X-cut lithium niobate crystal growth method as described in any one of claims 1 to 8.

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